As is well known, outboard motors for use in powering watercraft include an engine powering a water propulsion apparatus such as a propeller. These outboard motors have a cowling in which is positioned the engine. In order to keep the outboard motor small in dimension, the engine must have a very compact arrangement.
These engines typically include a coolant system which routes water drawn from the body of water in which the motor is positioned through the engine to cool the engine. It is most common to route the coolant through the cylinder block, cylinder head, and then through an exhaust manifold and/or exhaust pipe cooling jacket before discharging the coolant back to the body of water.
This coolant path has the disadvantage that the exhaust manifold is often not adequately cooled, such that heat is transferred therefrom to other engine components and the incoming air. At the same time, any coolant path which routes the coolant through the exhaust manifold in a manner which provides a higher rate of cooling must not do so at the expense of inadequately cooling the remainder of the engine, and must not require the coolant to pass through to circuitous of a route which results in poor coolant flow efficiency.
An outboard motor powered by an internal combustion engine and including an improved coolant system is desired.